Protective enclosure

ABSTRACT

An enclosure which provides protection from the blast of a high temperature explosion, as well as from the thermal effects of a surrounding fire on a metal structure, the enclosure including at least one sidewall having a rigid metal structure and forming an envelope with a metal beam or beams situated inside the envelope, the envelope having a width between 10 and 50 cm and defining a free volume for containing water.

FIELD OF THE INVENTION

[0001] This invention relates to an enclosure which provides protection from the blast of an explosion or a thrust resulting from a high temperature flame, as well as from the thermal effects of a surrounding fire on a metal structure.

PRIOR ART

[0002] Fire-protection elements (which are flexible, lightweight or substantially flexible) exist which surround a valve or pipe of a chemical or petrochemical installation, etc. Even if these elements enable the thermal effect of fires or conflagrations to be resisted, they are not capable of resisting the blast from an explosion.

[0003] The use has been proposed (for example by document WO02/07298 1) of flexible sacks or bags which are filled with water and placed on top of each other to form a protection against the blast from an explosion.

[0004] The bond joining the sacks or bags of water to each other is insufficient to resist the hot blast from an explosion in a gas conversion installation. Moreover, as soon as a temperature higher than about 100° C. is reached in the sacks or bags, there is a risk of explosion of the sacks or bags, which then results in collapse of the wall.

[0005] A wall of sacks or bags of water is only capable of forming a protection over a short time interval. Finally, the use of bags requires daily inspections and the frequent replacement of defective bags. This renders the use of sacks or bags filled with water unsuitable for use in industrial installations.

[0006] Protective constructions made of reinforced concrete are also known which are capable of resisting the blast of an explosion. However, such constructions are not capable of resisting the prolonged thermal effects of a fire or conflagration, due to the expansion of the concrete reinforcement, for example. In fact, the temperature increases progressively in the materials used and reduces their properties and mechanical strength all the more. Furthermore, excessive temperatures can occur in the interior of the enclosure after a certain time of exposure to fire. Constructions such as these are extremely heavy and cannot be dismantled quickly when necessary.

[0007] The object of the present invention is to create a protective enclosure capable of resisting the blast from an explosion or the thrust which results from a high temperature flame, as well as resisting the thermal effects of a surrounding fire, for more than 30 minutes, for example, particularly for more than 60 minutes, or even much more. The enclosure defines a protected chamber having a volume larger than 1 m3, particularly having a volume between 2 and 50 m3, for example between 2 and 30 m3, such as a volume of 3, 5, 8, 10, 15 m3, 20 m3, etc. The enclosure is preferably easy to install and dismantle without necessitating heavy equipment.

SUMMARY OF INVENTION

[0008] The enclosure according to the invention comprises:

[0009] an enclosure comprising one or more sidewalls and a roof which define an internal chamber,

[0010] one or more bases acting as a support to at least part of the sidewall or sidewalls.

[0011] The enclosure according to the invention is characterised in that:

[0012] at least the sidewall or sidewalls comprise a rigid metal structure forming an envelope comprising a metal beam or beams, said envelope having a thickness between 10 and 50 cm (advantageously between 20 and 50 cm) and defining a free volume for containing a medium capable of changing its phase (preferably at a temperature of less 150° C., for example at a temperature between 50 and about 100° C.), particularly an aqueous medium (such as water or an aqueous solution), said free volume corresponding to at least 50% of the total volume of the envelope.

[0013] The envelope comprises:

[0014] at least one opening for the removal of vapour and an opening for supplying water or an aqueous solution to the envelope, and

[0015] at least one means of removal to permit water to be removed from the internal chamber in the event of leakage of the envelope.

[0016] The envelope or each envelope is advantageously made of steel, advantageously of stainless steel, and has a free volume capable of containing water or an aqueous solution of at least 0.5 m3, for example of at least 1 m3, 1.5 m3, 2 m3, 3 m3, 5 m3, or even more. Once filled or partly filled with water, the envelope or envelopes ensure that the enclosure is of sufficient weight in order to counteract a displacement thereof following a blast.

[0017] The enclosure preferably comprises a plurality of distinct envelopes connected to each other by one or more ducts suitable for permitting the passage of water or of an aqueous solution from one envelope to another envelope by the principle of communicating vessels.

[0018] According to one embodiment, the enclosure is associated with a water supply and a control device for adjusting the level of water or aqueous solution in the envelope or envelopes.

[0019] According to one advantageous feature, the envelope or envelopes is associated with a means for preventing frost formation. A means such as this can be an electrical or heating resistance capable of maintaining the water present in the envelope or envelopes at a temperature higher than 0° C.

[0020] According to a feature of one embodiment, each sidewall is associated with at least one buttress which extends in the chamber and which is supported on a base, said buttress being capable of withstanding an external thrust on the wall.

[0021] For example, the sidewall or sidewalls can comprise an insulating layer facing the exterior of the enclosure with respect to an envelope adjacent to said insulating layer.

[0022] According to an advantageous feature of one embodiment, the wall or walls comprise an envelope comprising a metal structure to which one or more buttresses is/are attached.

[0023] The enclosure advantageously comprises one or more sidewalls which define a substantially circular external shape, or which define a substantially polygonal external shape with at least 5 sides, advantageously with least 6 sides, preferably with at least 8 sides.

[0024] According to one advantageous embodiment, substantially the entire bottom edge of the wall or walls extends in a channel or recess of a base or in channels of adjacent bases. The channel or recess is preferably associated with a duct for removing water from the enclosure.

[0025] According to one particular embodiment, the wall or walls comprise, at least from the outside to the inside of the internal chamber:

[0026] a protective plate, advantageously made of steel, particularly made of stainless steel,

[0027] a layer of thermal insulation, advantageously formed by a rigid or semi-rigid insulating material, said layer having a thickness of at least 20 mm, advantageously between 30 mm and 200 mm, preferably between 40 mm and 100 mm,

[0028] an envelope comprising a metal structure or reinforcement joined to a buttress or buttresses, said envelope being adapted for containing water or an aqueous solution and having a thickness between 10 and 50 cm.

[0029] The envelope preferably comprises a metal wall facing the layer of insulation and a metal wall facing the interior of the internal chamber, said metal walls being joined to each other by metal I-beams. The metal walls advantageously have a thickness of at least 4 mm, more advantageously between 5 and 30, particularly between 8 and 20 mm. I-beams advantageously form lateral edges of the envelope. The metal walls and the I-beams are advantageously welded together.

[0030] The enclosure according to the invention advantageously comprises a duct for supplying fresh air to the chamber and a duct for removing air from the chamber. The supply duct and the removal duct preferably pass under the bottom level of a wall.

[0031] The enclosure can be equipped with means for controlling the quantity of water present in the envelope and/or for maintaining at least a minimum level of water in the envelope.

[0032] According a particular feature of one particular embodiment, the enclosure comprises:

[0033] one or more envelopes of one or more sidewalls, said envelope(s) defining a free volume suitable for receiving water or an aqueous solution,

[0034] one or more reservoirs of a liquid aqueous medium situated inside the internal chamber, and

[0035] at least one means for supplying liquid aqueous medium from one or more reservoirs to the envelope or envelopes of the sidewall or sidewalls, wherein the volume of the reservoir corresponds to at least 50%, particularly to at least 100%, for example from 150% to 500%, of the free volume of the envelope or envelopes.

[0036] According to another important feature, the enclosure comprises a door mounted on hinges having a swivelling axis situated in the internal chamber. A door such as this permits ease of access to the internal chamber whilst ensuring excellent protection for the hinges, thus enabling any deterioration thereof to be prevented. The present door is advantageously substantially square or rectangular in shape, with sidewalls which are substantially parallel to the swivelling axis. The sidewall furthest from the swivelling axis has a shape which is appropriate for permitting a swivelling movement of the door, but which also permits said wall to contact an edge of a fixed or non-moveable wall.

[0037] The door swivels advantageously outside of the chamber, so as to leave more space free in the chamber for the equipment(s) to be protected.

[0038] According to an advantageous feature of one embodiment, the removal of vapour from the envelope comprises a means which counteracts the removal of vapour when there is a pressure in the envelope which is lower than a defined pressure. In particular, the means which counteract the removal of vapour from the envelope is selected from the group comprising valves, bursting discs and combinations thereof.

[0039] The invention also relates to the protection, by means of an enclosure of the invention, of at least one component of an installation which could accidentally be subjected to considerable fire and blast. The installations concerned can be units for processing combustible and/or explosive gas, particularly units for the liquefaction, gasification, expansion and/or compression of gas, such as natural gas (methane), propane, hydrogen, etc. The invention also relates to chemical or petrochemical installations, at least one component of which is placed in an enclosure of the invention.

[0040] Particular features and details of the invention follow from the detailed description given below, in which reference is made to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings are as follows:

[0042]FIG. 1 is a vertical sectional through a substantially cylindrical enclosure according to the invention;

[0043]FIG. 2 is a partial horizontal section (along line 1′-11) of the enclosure of FIG. 1;

[0044]FIG. 3 is a sectional view of a wall;

[0045]FIG. 4 is a sectional view of a detail of the enclosure of FIG. 1;

[0046]FIG. 5 is a partial horizontal section through a variant of an enclosure of the invention;

[0047]FIG. 6 is a view of a detail of a wall;

[0048]FIGS. 7 and 8 are schematic views of an enclosure of the invention (horizontal cross section) with its door in open position and in closed position;

[0049]FIG. 9 is a cross section view of the enclosure of FIG. 8 along the line IX-IX;

[0050]FIG. 10 is a cross section view of the enclosure of FIG. 7, along the line X-X;

[0051]FIG. 11 is a cross section view of the enclosure of FIG. 8 along the line XI-XI.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0052] The enclosure of FIG. 1 is a substantially cylindrical, closed enclosure 1, in which a suitable door 2 (of the type illustrated in FIG. 4, for example) can be disposed to provide access to the interior, and which comprises a removable roof 3 to enable major work to be carried out.

[0053] The protective enclosure 1 comprises a vertical, one-piece wall 4 or a series of walls which are joined to each other to permit the installation and dismantling of the enclosure. For example, in the embodiment illustrated, the circular wall 4 comprises a series of wall parts 4A, 4B joined to each other by a junction piece J. A bottom or anchoring base 5 serves as the basis or foundation for the wall 4. A rapid-opening access door 6 is provided in the vertical wall 4 (see FIG. 4). A vent system 7 permits the removal of undesirable substances which would accumulate in the enclosure and/or of gases or vapours formed during the phase transition of a product present in the wall. Another vent suitable for removing material which has undergone its phase transition can be provided, if necessary.

[0054] The walls 4 of the enclosure 1 are formed by at least one wall or external metal sheet 40 made of stainless steel or refractory having a thickness of 0.5 to 10 mm, for example (e.g. of 1 to 2 mm), an insulating layer 41 which is resistant to high temperatures, an envelope 42 intended to receive a substance or material M capable of exhibiting a phase transition below a restricted temperature, for example at a temperature between 50 and about 100° C. A low-temperature insulating layer can be added, if necessary, along the internal side of the envelope. Depending on the embodiment, the bottom and the roof 3 can be constructed in the same manner as the wall 4.

[0055] The envelope 42 is formed by a structure comprising beams 43, which are advantageously I-beams (vertical and horizontal beams, possibly with one or more cross-bracing elements), an internal metal wall 44 made of steel (for example stainless steel) facing the internal chamber in which the material to be protected is situated, and a wall 45 made of steel (for example stainless steel) facing the insulating layer 41. The envelope 42 is filled with water or an aqueous solution. The phase transition of water enables the envelope and parts in contact with the envelope to be maintained at a substantially constant temperature, by virtue of the use of calories passing through the wall for evaporation until the water present in the envelope is consumed. The envelopes 42 containing water and the mechanically rigid beams 43 therefore remain at a substantially constant temperature, of about 100° C., during the evaporation phase. It is therefore possible to maintain the mechanical (or even electrical) properties compatible with the envisaged requirements. The coefficients of expansion, the creep limits, and the tensile, compressive, flexural, torsion and shear strengths, as well as all the properties which result therefrom, are maintained within the specified limits which are acceptable for the application.

[0056] Instead of allowing heat to propagate towards the interior of the enclosure, a storage device such as this is advantageously combined with a venting system 7 for dissipating heat, in order to maintain an acceptable, predetermined temperature there.

[0057] The envelope 42 has a thickness or width E between 10 and 50 cm, for example, particularly between 20 and 50 cm. The weight of the water present in the envelopes thus participates in maintaining the enclosure in place despite the blast.

[0058] The envelopes thus serve to absorb and dissipate calories. Envelopes such as these enable enclosures to be constructed which are less thick, and which are therefore easier to handle, less costly, dismantleable and light, etc, when they are not filled with water. The envelopes also enable a constant, pre-calculated stability to mechanical stresses to be maintained, and also enable the temperature in the interior of the enclosure to be controlled at the desired level. Moreover, once the envelope is filled with water it provides a weight or foundation which is sufficient for the enclosure.

[0059] The enclosure 1 is designed to withstand high external pressures.

[0060] For this purpose, the bottom edge of the walls 4 is placed in a recess 5A in the concrete base 5. Moreover, buttresses 10 are attached to the envelope of the walls, and said buttresses 10 are supported on the base 5. The buttresses are situated on the inside of the enclosure 1, so that they are protected from thermal effects by the envelopes 42. The mechanical properties of the buttresses 10 can thus be ensured even if the enclosure is subjected to a continuous fire.

[0061] The envelope 42 is kept cold by the phase transition of the material situated in it, and thus constitutes an envelope which is strongly resistant to high external pressures. In fact, the envelope itself, its anchorage in the ground or base 5, and the sloping stanchions or buttresses 10 attached to the wall 44 of the envelope 42 (buttresses which withstand external forces) are maintained at a given maximum temperature by virtue of the phase transition of the material, during the entire duration of the phase transition. The mechanical strength of these parts, particularly of the buttresses 10, can be calculated and designed for these temperatures (for example for a corresponding temperature without risk of deterioration during the time of heating such as that which would occur in a conventional thermal insulation system).

[0062] Anchorage and embedding of the wall or walls in the base 5 is achieved by inserting the bottom part of the enclosure 4 in the recess or channel 5A. Thus, the outside wall 40, the insulating layer 41 and the envelope 42 containing the material capable of exhibiting a phase transition (water) are embedded at the bottom in the concrete base 5, which is installed in the ground or on a stable, perfectly rigid foundation, such as a solid pipeline. The lower reinforcements (beams 43) and buttresses 10 of the envelope 42 are fixed to said base 5. The upper part of the wall 4 is stiffened by the roof 3 which is mounted on and fixed to the internal walls 44 (by bolts and nuts) whilst being removable. The system for attaching the roof to the wall 4 is thus situated in the chamber CI and is therefore protected from fire.

[0063] In the embodiment shown in FIG. 1, the walls of the enclosure 1 form a cylindrical wall.

[0064] The walls of the envelope are advantageously shaped so that the latter is as continuous as possible along its perimeter, in order to ensure an external surface which is the smallest possible and/or the most aerodynamic possible. Therefore, a polygonal profile can also be used (FIG. 5) instead of a circular profile (FIG. 2). This mode of design enables a good resistance to high external pressures (of dynamic origin for example) to be ensured, and also enables pronounced joints to be avoided, and therefore enables problems of leak-tightness between the different parts forming the wall of the enclosure to be avoided. It also enables the assembly to be stiffened better, and results in an improved mechanical resistance to external pressures. The various wall sections are joined by means of screwed joints and/or by welding.

[0065] The enclosure is advantageously provided with an access door 11 (FIG. 4).

[0066] In substantially one-piece enclosures, it is advantageous to provide an access door for persons, for inspection, maintenance, etc.

[0067] The door 11 is advantageously designed so as to reduce or prevent thermal bridges and losses of leak-tightness between the hot part (the outside) and the cold part (the internal chamber CD. For this purpose, for example, a door 11 can be used which moves by direct displacement (X) perpendicular to the plane of the supporting wall 4, said door being mounted on a movable trolley or being capable of being mounted on a trolley 12.

[0068] The envelopes 42 contain one or more materials capable of changing their state when they are subjected to a rise in temperature.

[0069] The substances used are preferably selected according to their change of state temperature and their capacity for storing calories when a change of state occurs. Their ease of use and their cost is also taken in consideration. The substances (M) are advantageously substantially flameproof, as are their transformation products.

[0070] Water is the substance which best fulfils these criteria. At its boiling temperature of 100° C., most materials retain the majority of their important mechanical properties. Moreover, antifreeze and anti-corrosion additives can easily be added to water.

[0071] In the walls of the enclosure, a layer of insulation is used which is intended to reduce the quantity of heat or calories which have to be stored by the material which changes its state.

[0072] A rigid or semi-rigid insulation which is not deformed under the effect of external pressures is preferably used. It is fixed to the walls of the envelope (towards the outside) whilst taking care to minimise the effect of thermal bridges. An insulation is preferably selected which withstands high temperatures and which has a thermal conductivity related to its potential for storing heat which can be dissipated and which is present in the envelope.

[0073] The enclosure is advantageously aerated. For example, an assembly of two ducts 13, 14 ending respectively at a ventilation orifice or shaft 7 and a cool air aspiration orifice 6 permit natural or forced ventilation (by virtue of a fan or blower 15) of the interior volume in order to eliminate harmful or explosive substances which would otherwise accumulate therein. These conduits 13, 14 extend at least partially in the ground so as to pass through the base 5 below the walls 4, which avoids the necessity of forming passageway openings in the walls, such openings resulting in the mechanical weakening of the walls and in leak-tightness problems therefor.

[0074] In the embodiment illustrated, the removal of vapours or other products resulting from the phase transition can be effected via the chamber CI. In this case, the envelope 42 has one or more openings 42bis at its top part.

[0075] In the case of water, the vapour formed in fact spreads inside the chamber CI of the enclosure and serves to dilute the existing atmosphere before being removed by the ventilation duct or ducts 13. It is also possible to discharge the products of transformation directly to the outside or via an additional reheating circuit installed in the hot part of the enclosure wall, which extracts all the more calories.

[0076] The removal of vapours is effected by virtue of the duct 13, which has an end 13A suitable for collecting hot vapours in the vicinity of the roof or the top part of the enclosure, and a non-return or check valve 13B.

[0077] The volume of the internal chamber ranges, for example, between 1 and 50 m3, such as 5, 10, 15, 20 or 30 m3, for example.

[0078] The enclosure is advantageously provided with means for collecting and removing water of condensation and with means for protecting devices placed in the chamber from the effects of water of condensation. Examples of such means include the pipelines 60, 61 which pass through the base. The pipeline 60 is suitable for removing water which may be present in the channel 5A.

[0079] When the enclosure comprises a plurality of adjacent or substantially adjacent envelopes, it is advantageous to provide one or more ducts or passages 62 to form a communication between the envelopes in order to permit the passage of water from one envelope to another envelope by the effect of communicating vessels.

[0080] The envelope 42 is advantageously provided with a passage 63 a fluidically connected to a water supply 63 in order to fill the envelope as needed. The envelope 42 is also advantageously provided with a control device 63 b, which, for example, ensures a water level between a minimum level and a maximum level (said control device controlling the inflow of water into the envelope). The envelope 42 is preferably associated with an overflow 64 to prevent the water level in the envelope from exceeding a maximum level. Depending on the installation of the enclosure, it may be useful to provide systems for the addition of an antifreeze product to the envelope and/or to provide a heating system (for example an electrical resistor 65 situated in the base of the envelope 42). The electrical resistor can be controlled, for example, in order to ensure a mean temperature of the water present in the envelope of at least 2° C., for example between 2 and 5° C., and/or to prevent the operation of the resistor if the latter is not in contact with water.

[0081] It is also possible to provide a circulating pump (placed in the interior of the envelope, for example) to effect movement of the water or liquid present in the envelope.

[0082]FIG. 7 is a schematic illustration (in horizontal cross-section) of part of an enclosure having sidewalls 4 and a door 6 in an open position (partial open position).

[0083] The sidewalls 4 form an aperture 100 defined between the two side edges 101, 102 and between a bottom edge 1031 and a top edge 103S. Buttresses 10 are provided in the vicinity of the side edges 101, 102 and are each formed by three flat bars 104, 105, 106 which are attached to each other (by bolts, by weld points or lines, etc.) Bar 104 and bar 105 form an L-shaped angle which extends vertically, the vertex 107 of the elbow being adjacent to an internal vertical wall. Bar 106 itself extends in a vertical plane but has an axis 106A which is inclined with respect to the vertical axis. A buttress 10 serves to bear hinges 108 (3, 4 or more, for example) to which the door 6 is attached. The hinges 108 are situated in the internal chamber CI of the enclosure and have the same swivelling axis 109. A series of curved arms 108A extend between the hinges 108 and the door 106. The opening of the door 6 can be operated against the action of one or more springs 108B.

[0084] In cross-section, the bottom edge 1031 is in the shape of a stairway or flight of steps, while the upper edge 103S forms with the cover 153 a stairway shape. The distance 111 separating the stairway shapes of the edges 1031, 103S from each other is lower on the side of the internal chamber CI than the distance 112 separating said stairway shapes of the edges 1031, 103S on the external side.

[0085] The side edges of the window themselves are suitable for enabling the door to be opened and closed simply by rotation.

[0086] On its external face, the door 6 can be provided with one or more extensions intended to cover the sidewalls 4 and/or bottom/upper edges when the door 6 is in its closed position.

[0087] The bottom part of the bottom edge 1031 is placed in the channel 130 of the base 5, said channel 130 being connected to drain channels or a drain 131 by a pipeline 132.

[0088] The sidewalls 4 and the door 6 comprise an envelope 140, 141 (made of stainless steel plates welded together, with I-beams 200 therebetween, said beams having a perforated web for enabling the free flowing of water and/or water vapor from one side of the web towards the other side of the web, while the wings of the beams are attached at least partly to steel plates) suitable for containing water in liquid form, a layer of thermal insulation 142 (rigid, for example), and an external protective wall 143.

[0089] The envelopes 140, 141 are provided with a valve 144 which controls the release, in the chamber CI, of vapour which may possibly be formed in an envelope, and a bursting disc 145, said disc being ruptured if the pressure in the envelope is too high. When the envelopes 140 are connected therebetween with pipes 170,171 for enabling passage of water and water vapor from one envelope towards another envelope, only one envelope 140 can be provided with a control valve 144 and a bursting disc 145.

[0090] The enclosure also comprises a reservoir 150 situated in the internal chamber CI. This reservoir advantageously has a volume which corresponds to at least the sum of the free volumes of all the envelopes 140, 141 which are capable of containing water.

[0091] This reservoir 150 comprises a submerged pump 151 which is capable of forcing water into the pipeline 152, the top part of which extends in the vicinity of the roof 153. Pipes 154 and hoses 155 connect the different envelopes 140,141 to the pipeline 152. The hose 155 enables a connection to be maintained between the envelope 140 and the pipeline 152 during a swivelling movement of the door 6.

[0092] The pipes 154 and hoses 155 are provided with controlled valves 157 to ensure the supply of water to an envelope or envelopes when the water level in said envelope or envelopes is lower than a defined level.

[0093] The bottom part of the envelope 141 of the door 6 is advantageously connected by a hose 158 to a controlled valve 159, to enable the water in the envelope 141 to be at least partly emptied, by gravity or via a communicating vessel or by means a sucking pump (such as a pump 159A), into the reservoir 150.

[0094] An emergency or reserve supply of electrical energy 161 is advantageously provided in the internal chamber CI of the enclosure for the operation of the pumps 151, 159A and the control system 160 for the pump and valves.

[0095] The volume of the reservoir 150 is greater than 1 m3, such as 2, 4, 5 or 10 m3, or even greater.

[0096] The envelopes 140 of the three side walls 4 are connected by means of pipes 170, whereby water from one envelope can flow towards another envelope by gravity of by the principle of communicating vessels. Pipes 171 are also provided so as to enable a free passage of water vapour from one envelope towards another envelope 140. The pipes 171 are located near the cover 153, while the pipes 170 are located near the base 5.

[0097] The envelope 140 can be provided with an overflow 172, returning water above a predetermined maximum authorised water level 173, said overflow 172 returning water to the reservoir 150.

[0098] The reservoir 150 is advantageously provided with a water supply 174 with a controlled valve 175, as well as of an overflow 176 conducting excessive water of the reservoir into the drain 131. The overflow 176 is also connected to an outlet pipe 198 with a controlled outlet valve 199, for running off the water of the reservoir 150.

[0099] The cover 153 is also provided on its inner face with an insulation layer 142.

[0100] The enclosure of FIG. 7 is advantageously provided with aerating means 6,7,13,13A, 14 such as the door, vent system and/or ducts disclosed for the embodiment of FIG. 1. 

What I claim is:
 1. An enclosure which provides protection from the blast of an explosion or a thrust resulting from a high temperature flame, as well as from the thermal effects of a surrounding fire on a metal structure, said enclosure comprising: a rigid enclosure comprising at least one sidewall and a roof which define an internal chamber, at least one base serving to support at least part of the sidewall, wherein the sidewall comprises a rigid metal structure forming an envelope comprising at least one metal beam situated inside the envelope, said envelope having a thickness between 10 and 50 cm and defining a free volume suitable for containing an aqueous medium capable of changing into a vapour phase at a temperature of less 150° C., said free volume corresponding to at least 50% of the total volume of the envelope, wherein the envelope comprises at least one means of removal for removing vapour created in the envelope, and a passage adapted for connection to a supply means for supplying an aqueous medium selected from the group comprising liquid aqueous media, solid aqueous media, semi-solid aqueous media and combinations thereof, in the envelope, and wherein the enclosure comprises at least one means of removal which enables water to be removed from the internal chamber in the event of leakage of the envelope.
 2. The enclosure of claim 1, which comprises: a rigid enclosure comprising a plurality of sidewalls and a roof which define an internal chamber, at least one base serving to support at least part of the sidewalls, wherein the sidewalls each comprise a rigid metal structure forming an envelope comprising at least one metal beam situated inside the envelope, said envelope having a free volume corresponding to at least 50% of the volume of the envelope.
 3. The enclosure of claim 1, for which the envelope is suitable for containing a medium selected from the group consisting of water in liquid form and liquid aqueous solutions.
 4. The enclosure of claim 1, wherein the envelope of at least one sidewall is made of steel, and comprises a free volume of at least 0.5 m3 capable of containing an aqueous medium.
 5. The enclosure of claim 1, wherein the envelope is made of stainless steel.
 6. The enclosure of claim 1, wherein for each of the sidewalls the envelope is made of steel, and has a free volume of at least 0.5 m3 capable of containing an aqueous medium.
 7. The enclosure of claim 1, which comprises a plurality of distinct envelopes connected to each other by at least one passage capable of permitting the passage of a liquid aqueous medium from one envelope to another envelope by the principle of communicating vessels.
 8. The enclosure of claim 1, which is associated with a water supply and a control device for adjusting the water level in the envelope of at least one sidewall, said envelope being associated with an overflow.
 9. The enclosure of claim 1 comprising a plurality of sidewalls, each comprising at least one envelope, said enclosure being associated with a water supply and with a control device for adjusting the water level in the envelopes of the sidewalls, said envelopes being associated with at least one overflow.
 10. The enclosure of claim 1, comprising: a reservoir of a liquid aqueous medium situated inside the internal chamber, and at least one means for supplying liquid aqueous medium from the reservoir to at least the envelope of one sidewall.
 11. The enclosure of claim 10, wherein the means for supplying the liquid aqueous medium from the reservoir to at least the envelope of one sidewall comprises at least one pump associated to a pipeline which extends between the reservoir and the envelope, and wherein the pump is controlled by a device which monitors the level of liquid aqueous medium in the envelope.
 12. The enclosure of claim 1, comprising: a plurality of sidewall envelopes, a reservoir of a liquid aqueous medium situated inside the internal chamber, and at least one means for supplying liquid aqueous medium from the reservoir to the envelopes of the sidewalls, wherein the volume of the reservoir corresponds to at least 50% of the free volume of the envelopes.
 13. The enclosure of claim 1, comprising: a plurality of sidewall envelopes, a reservoir of a liquid aqueous medium situated inside the internal chamber, and at least one means for supplying liquid aqueous medium from the reservoir to the envelopes of the sidewalls, wherein the volume of the reservoir corresponds to at least 100% of the free volume of the envelopes.
 14. The enclosure of claim 1, wherein the envelope of at least one sidewall is associated with a means for preventing the formation of frost or ice.
 15. The enclosure of claim 1 comprising a plurality of sidewalls, wherein each sidewall is associated with at least one buttress which extends in the chamber and which is supported on a base, said buttress being capable of withstanding an external thrust on the wall.
 16. The enclosure of claim 1, wherein at least one sidewall comprises an insulating layer facing the exterior of the enclosure with respect to an envelope adjacent to said insulating layer.
 17. The enclosure of claim 1 comprising a plurality of sidewalls with an envelope, wherein each sidewall comprises an insulating layer facing the exterior of the enclosure with respect to the envelope of the wall concerned which is adjacent to said insulating layer.
 18. The enclosure of claim 1, wherein at least one sidewall comprises an envelope comprising a metal structure to which is attached at least one buttress.
 19. The enclosure of claim 1, wherein at least one sidewall comprises an envelope comprising a metal structure to which is attached a plurality of buttresses.
 20. The enclosure of claim 1 comprising a plurality of sidewalls, wherein at least one sidewall comprises an envelope comprising a metal structure to which at least one buttress is attached.
 21. The enclosure of claim 1, which comprises at least one sidewall which defines a substantially circular external shape.
 22. The enclosure of claim 1, which comprises a plurality of sides which define a substantially polygonal external shape with at least 5 sides.
 23. The enclosure of claim 1, which comprises a plurality of sides which define a substantially polygonal external shape with at least 6 sides.
 24. The enclosure of claim 1, which consists of a plurality of sides which define a substantially polygonal external shape with at least 8 sides.
 25. The enclosure of claim 1 comprising at least one sidewall with a bottom edge, wherein substantially the entire bottom edge of the sidewall extends in a channel in at least one base.
 26. The enclosure of claim 1 comprising a plurality of sidewalls having a bottom edge, wherein substantially the entire bottom edge of each of the sidewalls extends in a channel in at least one base.
 27. The enclosure of claim 25, wherein the channel is associated with a duct for removing water from the enclosure.
 28. The enclosure of claim 26, wherein the channel is associated with a duct for removing water from the enclosure.
 29. The enclosure of claim 1, wherein the sidewall comprises, at least from the outside to the inside of the internal chamber: a protective plate, a layer of thermal insulation having a thickness of at least 20 mm, an envelope comprising a metal structure joined to at least one buttress, said envelope being suitable for containing a liquid aqueous medium having a thickness between 10 and 50 cm.
 30. The enclosure of claim 2, wherein the sidewall comprises, at least from the outside to the inside of the internal chamber: a protective plate, a layer of thermal insulation having a thickness of at least 20 mm, an envelope comprising a metal structure joined to at least one buttress, said envelope being suitable for containing a liquid aqueous medium having a thickness between 10 and 50 cm.
 31. The enclosure of claim 29, wherein: the protective plate is made of steel, the layer of thermal insulation is made of a material selected from the group consisting of rigid insulating materials, semi-rigid insulating materials and combinations thereof, and the layer of insulation has a thickness between 30 mm and 200 mm.
 32. The enclosure of claim 1, wherein the sidewall comprises, at least from the outside to the inside of the internal chamber: a protective plate, a layer of thermal insulation having a thickness of at least 20 mm, an envelope comprising a metal structure joined to at least one buttress, said envelope being suitable for containing a liquid aqueous medium having a thickness between 10 and 50 cm, the envelope comprising a metal wall facing the layer of insulation and a metal wall facing the interior of the internal chamber, said metal walls being joined to each other by metal I-beams.
 33. The enclosure of claim 32, wherein the metal walls have a thickness of at least 4 mm.
 34. The enclosure of claim 1, wherein the sidewall comprises, at least from the outside to the inside of the internal chamber: a protective plate, a layer of thermal insulation having a thickness of at least 20 mm, an envelope comprising a metal structure joined to at least one buttress, said envelope being suitable for containing a liquid aqueous medium having a thickness between 10 and 50 cm, the envelope comprising a metal wall facing the layer of insulation and a metal wall facing the interior of the internal chamber, said metal walls having a thickness between 5 and 30 mm and being joined to each other by metal I-beams.
 35. The enclosure of claim 1 which comprises a duct for supplying air to the chamber and a duct for removing air from the chamber.
 36. The enclosure of claim 35, wherein the supply duct and the removal duct pass under the bottom level of a sidewall.
 37. The enclosure of claim 1, wherein the aqueous medium which is capable of changing phase is a medium capable of changing phase below 110° C.
 38. The enclosure of claim 1, said enclosure comprising a door mounted on hinges having a swivelling axis situated in the internal chamber.
 39. The enclosure of claim 1, wherein the removal of vapour from the envelope comprises a means which counteracts the removal of vapour when there is a pressure in the envelope which is lower than a defined pressure.
 40. The enclosure of claim 1, wherein the means which counteracts the removal of vapour from the envelope is selected from the group consisting of valves, bursting discs and combinations thereof.
 41. A gas conversion installation comprising at least one unit selected from a liquefaction unit, a gasification unit, an expansion unit, a compression unit and a combination thereof, wherein at least one component of the installation is in an enclosure which provides protection from the blast of an explosion or a thrust resulting from a high temperature flame, as well as from the thermal effects of a surrounding fire on a metal structure, said enclosure comprising: a rigid enclosure comprising at least one sidewall and a roof which define an internal chamber, at least one base serving to support at least part of the sidewall, wherein the sidewall comprises a rigid metal structure forming an envelope comprising at least one metal beam situated inside the envelope, said envelope having a thickness between 10 and 50 cm and defining a free volume suitable for containing an aqueous medium capable of changing into a vapour phase at a temperature of less 150° C., said free volume corresponding to at least 50% of the total volume of the envelope, wherein the envelope comprises at least one means of removal for removing vapour created in the envelope, and a passage adapted for connection to a supply means for supplying an aqueous medium selected from the group comprising liquid aqueous media, solid aqueous media, semi-solid aqueous media and combinations thereof, in the envelope, and wherein the enclosure comprises at least one means of removal which enables water to be removed from the internal chamber in the event of leakage of the envelope.
 42. An installation according to claim 41, wherein the enclosure comprises: a rigid enclosure comprising a plurality of sidewalls and a roof which define an internal chamber, at least one base serving to support at least part of the sidewalls, wherein the sidewalls each comprise a rigid metal structure forming an envelope comprising a metal beam or beams situated inside the envelope, said envelope having a free volume corresponding to at least 50% of the volume of the envelope.
 43. An installation according to claim 42, wherein the envelope of at least one sidewall is made of steel, and comprises a free volume of at least 0.5 m3 capable of containing an aqueous medium.
 44. An installation according to claim 41, wherein the enclosure comprises a plurality of distinct envelopes connected to each other by at least one passage capable of permitting the passage of a liquid aqueous medium from one envelope to another envelope by the principle of communicating vessels.
 45. An installation according to claim 41, wherein the enclosure comprises: a reservoir of a liquid aqueous medium situated inside the internal chamber, and at least one means for supplying liquid aqueous medium from the reservoir to at least the envelope of one sidewall.
 46. An installation according to claim 41, wherein the enclosure comprises at least one sidewall which defines a substantially circular external shape.
 47. An installation according to claim 41, wherein the enclosure comprises a plurality of sides which define a substantially polygonal external shape with at least 5 sides.
 48. An installation according to claim 41, wherein the enclosure comprises at least one sidewall with a bottom edge, wherein substantially the entire bottom edge of the sidewall extends in a channel in at least one base.
 49. An installation according to claim 48, wherein the channel is associated with a duct for removing water from the enclosure.
 50. An installation according to claim 41, wherein the sidewall comprises, at least from the outside to the inside of the internal chamber: a protective plate, a layer of thermal insulation having a thickness of at least 20 mm, an envelope comprising a metal structure joined to at least one buttress, said envelope being suitable for containing a liquid aqueous medium having a thickness between 10 and 50 cm, the envelope comprising a metal wall facing the layer of insulation and a metal wall facing the interior of the internal chamber, said metal walls having a thickness between 5 and 30 mm and being joined to each other by metal I-beams.
 51. An installation according to claim 41, said enclosure comprising a door mounted on hinges having a swivelling axis situated in the internal chamber.
 52. An installation according to claim 41, wherein the removal of vapour from the envelope comprises a means which counteracts the removal of vapour when there is a pressure in the envelope which is lower than a defined pressure, said means counteracting the removal of vapour from the envelope being selected from the group consisting of valves, bursting discs and combinations thereof. 